Pros and Cons of Studies ✔️ Flashcards
What is a Systematic Review?
What is a Meta-Analysis?
A Systematic Review presents all the published findings on a specific research question through protocol driven review of the literature
A Meta-analysis is the statistical analysis of several trials represented by a forest plot
What are the advantages of a Systematic Review?
- Separate studies may have examined different sample populations which when analysed together give a more accurate assessment of true population
- Aggregation of numbers leads to increased power and therefore a reduction in Type II Error, i.e. false negative
- Review enables integration of all existing data into a single resource which is less time consuming for clinicians
- May identify research gaps or concerns in methodology which can be used to improve future research
- Allows clinical relevance of existing literature to become apparent reducing systematic bias as benefits seen from meta-analysis less likely due to chance
What are the disadvantages of a Systematic Review?
- Direct comparisons of studies can be difficult if the methodology is too different e.g. inclusion / exclusion criteria
- Papers with negative results remain unpublished leading to publication bias
What is a Randomised Control Trial?
An Experimental trial where patients are randomly allocated to one intervention e.g. Drug A or Drug B. Patients should have an equal chance of being allocated to either group to eliminate the chance of bias
What are the advantages of a Randomised Control Trial?
- RCTs allow a temporal relationship between intervention and outcome to be made which allows the authors to show causation
- Confers a high level of evidence
- It allows the analysis of a very specific research question in a defined population group
- Process of randomisation eliminates selection bias and minimises confounding factors between groups
- Blinding can be used to eliminate performance bias (one group being treated to another due to investigator knowing allocations)
What are the disadvantages of a Randomised Control Trial?
- Can be expensive / time consuming
- Often funded by pharmaceutical companies who may have competing motives in finding a result
- Difficult to achieve adequate sample size and therefore study can be underpowered which means negative results may be invalid
- Selection of patients for the study based on likely participation / chance of success which can introduce bias into design, i.e. Volunteer Bias
What is a Cohort Study?
When groups are selected based on whether they have a particular exposure e.g. smoking and are then followed up over time to identify if they develop a particular outcome of interest e.g. lung cancer
What are the advantages of a Cohort Study?
- Can establish a temporal relationship demonstrating causal link between exposure and outcome
- Multiple outcomes can be measured
- Good for RARE EXPOSURES
- Estimate relative risk
- Can establish timing and directionality
- Ethically it is safe
What are the disadvantages of a Cohort Study?
- Require follow up for patients over a long duration - expensive
- Inefficient for rare outcomes which have a long latency period
- Large cohort is required which can be difficult to achieve in addition to high loss to follow up
- Exposure may be linked to a hidden confounder
What is a Case Control Study?
Patients divided into cases and controls. Relevant exposure is measured retrospectively and frequency of exposure between two groups is compared
What are the advantages of a Case Control Study?
- Good for RARE OUTCOMES
- Quick and cheap to conduct and can measure multiple exposures
- Requires fewer patient numbers than a cohort study
What are the disadvantages of a Case Control Study?
- Retrospective study so working with reverse causation – can’t be sure that the disease came after the exposure or vice versa
- Prone to recall bias
What are the advantages of Crossing Over in an RCT?
- All participants serve as own controls and error variance is reduced, thus reducing sample size needed
- All participants receive treatment (at least some of the time)
